Pipelines are being laid along the ocean floor in depths of water as deep as 3000 feet. The pipelines are subject to a variety of dangers including laying stresses, being laid across rock outcroppings, having to span valleys, and having equipment dropped on them. Any of these factors can cause a pipeline to leak. They may also leak due to manufacturing defects or errors in the connection processes at the surface.
When a pipeline begins to leak, it can cost an extremely high sum of money to try to bring it back to the surface. Cases have been known when an operator attempted to bring a shallow water pipeline to the surface for a repair, and caused several other leaks in doing so.
More typically in shallow water, divers are sent down with split clamp assemblies to clamp around the pipe, seal on the pipe, and act as a repair device. An excellent discussion of this was included in the November 1976 issue of the Oil & Gas Journal Magazine.
The ability to repair the pipeline is critical. If the leak cannot be stopped, the pipeline must be abandoned.
The ability to remotely repair a pipeline is needed to safely repair pipelines in diver depths of seawater, however, beyond approximately 1000 feet of water, the divers cannot make repairs at all. Beyond this depth, without the ability to make remote repairs, the expensive pipelines must simply be abandoned. The cost of a replacement pipeline in 1000-3000 feet of water is millions of dollars, and millions of dollars in deferred production.